file handling in java example programs | file IO in java ,

File I/O in Java

Java I/O stream in flow in data you can either read or you can write to.

It is used to perform read and write operations in file permanently. Java uses streams to perform these tasks. Java I/O stream is also called File Handling, or File I/O. It is available in java.io package.

Stream

A stream is a sequence of data. In Java, a stream is composed of bytes. It's called a stream because it is like a stream of water that continues to flow.

In Java, 3 streams are created for us automatically. All these streams are attached with the console.

1) System.out: standard output stream

2) System.in: standard input stream

3) System.err: standard error stream

the code to print output and an error message to the console.

System.out.println(“siple message”);

System.err.println(“error message”);

 the code to get input from console.

int i=System.in.read();

System.out.println(char)i);

OutputStream vs InputStream

The explanation of OutputStream and InputStream classes are given below:

OutputStream

Java application uses an output stream to write data to a destination; it may be a file, an array, peripheral device or socket.

InputStream

Java application uses an input stream to read data from a source; it may be a file, an array, peripheral device or socket.

Let's understand the working of Java OutputStream and InputStream by the figure given below.

java I/O file

OutputStream class

OutputStream class is an abstract class. It is the superclass of all classes representing an output stream of bytes. An output stream accepts output bytes and sends them to some sink.

Useful methods of OutputStream

Method	Description
1)public void write(int)throw Exception	is used to write a byte to the current output stream.
2)public void write(byte[])throw exception	Is used to write an array of byte to the current output stream.
3)public void flush()throw IO exception	flushes the current output stream.
4) public void close()throw IO Exception	Is used to close the current output stream.

 

OutputStream Hierarchy

java file handling

InputStream class

InputStream class is an abstract class. It is the superclass of all classes representing an input stream of bytes.

 

Useful methods of InputStream

Method	Description
1)public void abstract int read()throw IO exception	Reads the next byte of data from the input  stream.It returns-1 at the end of the file.
2)public void available()throw IO Exception	Returns a estimate of the number of bytes that can be read from the current input stream.
3)public void close()throw IO exception	Is used  to closed the current input stream.

 InputStream Hierarchy

java IO file handling